Krugman explained that he’d become an economist because of science
fiction. When he was a boy, he’d read Isaac Asimov’s “Foundation”
trilogy and become obsessed with the central character, Hari Seldon.
Seldon was a “psychohistorian”—a scientist with such a precise
understanding of the mechanics of society that he could predict the
course of events thousands of years into the future... He couldn’t predict individual
behavior—that was too hard—but it didn’t matter, because history was
determined not by individuals but by laws and hidden forces. “If you
read other genres of fiction, you can learn about the way people are
and the way society is,” Krugman said to the audience, “but you don’t
get very much thinking about why are things the way they are, or what might make them different. What would happen if ?”

With
Hari Seldon in mind, Krugman went to Yale, in 1970, intending to study
history, but he felt that history was too much about what and not
enough about why, so he ended up in economics. Economics, he found,
examined the same infinitely complicated social reality that history
did but, instead of elucidating its complexity, looked for patterns and
rules that made the complexity seem simple. Why did some societies have
serfs or slaves and others not? You could talk about culture and
national character and climate and changing mores and heroes and
revolts and the history of agriculture and the Romans and the
Christians and the Middle Ages and all the rest of it; or, like
Krugman’s economics teacher Evsey Domar, you could argue that if
peasants are barely surviving there’s no point in enslaving them,
because they have nothing to give you, but if good new land becomes
available it makes sense to enslave them, because you can skim off the
difference between their output and what it takes to keep them alive.
Suddenly, a simple story made sense of a huge and baffling swath of
reality, and Krugman found that enormously satisfying....

Krugman went to graduate school at M.I.T. “M.I.T. in the
mid-seventies was a sort of Athens of economics—everybody was there,”
he says. “And it was a golden age for clever little models.” Krugman
took a class with Rudiger Dornbusch and became interested in
international macroeconomics. Bretton Woods—the international system of
monetary control established by the Allies during the Second World
War—had just collapsed a few years earlier, floating exchange rates had
turned out to be much more volatile than anybody expected, and figuring
out why turned out to be a fantastically interesting puzzle.

Krugman
wrote his thesis on exchange rates, but another class, on international
trade, inspired him. “There was this kind of platonic beauty to the
whole thing,” he says. “I remember going through the two-by-two-by-two
model—two goods, two countries, two factors of production. The way all
these pieces fitted together into a Swiss-watch-like mechanism was
beautiful. I loved it.”...

There's lots of other stuff here: biographical and personal details (how he does his laundry on the road), how his political perspective has evolved, the evolution of his major economic contributions, how mathematical models can mislead, reflections on his professional productivity trajectory, and more.